Effective management and processing of e-mails has been a central concern for companies and Internet Service Providers (ISPs) for many years. Several solutions have been developed to deal with unsolicited e-mails, or spam. Most of these solutions use some algorithms, or some hand-crafted rules, for e-mail profiling and filtering but they are just partially effective and it is, usually easy to fake them (PCWorld, 2000). Most of these systems are intended to alleviate e-mail overload in open network environments, such as the Internet.
However, in corporate networks, e-mail overload does not come generally from spam, or junk mail, but more from irrelevant and unimportant business e-mail exchange between employees. Many employees in big corporations are overloaded by daily avalanches of internal e-mails from colleagues. This happens mostly to employees in middle management of large corporations who receive large amounts of unimportant e-mails from upper and lower corporate units.
There are some systems which are used for managing email and avoiding each user from receiving a large amount of trivial or irrelevant e-mail. The existing systems can be classified in three classes:                e-mail Filtering        The filtering systems are the most widely used for sorting important e-mails from unsolicited or junk mail (spam). There are spam filters which operate at the server and at the client level. They usually use some rule-based mechanisms to recognize junk mail and delete it, or reroute it to a specific folder for further processing. The filtering rules usually use either lists of unwanted mailing sources or apply some spam pattern detection technique to recognize massive flow of incoming e-mails with some specific pattern. These rules can be derived through automatic analysis of e-mail streams or manually whenever a mail system administrator notices a large attack in the mail system in which they see a lot of illicit mail or spam going to a lot of people all from one place.        Despite the wide deployment of spam filters by e-mail service providers, they can filter out only a fraction of the junk they are supposed to, according to a benchmark study (PCWorld, 2000). Further development of better filters which incorporate more intelligent technology is of primary importance. Such importance is dictated by the increasing cost of processing larger and larger amounts of e-mail, and by users overload with unsolicited mail.        e-mail Categorization        There are two main types of systems which offer such functionality which consists in automatic routing of e-mail at a server or at a client (user) level. Systems with predefined categories and systems which discover the categories through a categorization process which uses some clustering algorithm. In the case of predefined categories, the user specifies the categories (or classes) he/she wants to partition the mail box into, and then gives the system a few typical e-mail examples which represent each category (or class). These typical examples are used for system training using some machine learning algorithm which allows inferring decision rules for automatic classification of future incoming e-mails. In the second type of systems, the number and content of the categories are automatically discovered from the set of e-mails of a user's mail box. These systems define some similarity measure between documents (e-mails) and then group similar documents into clusters which are further refined either through merging several clusters or through splitting too general ones.        Both types of systems usually use various text mining technologies for document representation (usually a vector space), similarity measure (metrics) and category learning from examples using supervised or unsupervised machine learning algorithms.        Such systems can prove efficient for handling e-mail flows, for instance by defining specific categories of mails which are urgent, or topic-related, or group-related, etc. Although they might help to prioritize e-mail processing, they do not eliminate the overhead due to unimportant or irrelevant e-mail as they do not provide any measure of real importance to the user.        e-mail Size Limitation        The systems with such functionality allowed management of e-mails either based on the size of incoming and/or outgoing messages, or based on a predefined limit size of the user's mail box. Some systems allow to either block incoming or outgoing e-mails above some threshold size, or reschedule their routing to subsequent time to optimize bandwidth cost.        
Although the approaches presented above can alleviate problems related to large size, junk, or spam mail in an open network environment, they are of little use in corporate networks where most of the e-mail overload comes from unimportant and irrelevant mail exchange between employees. What is needed in corporate networks are mechanisms which regulate e-mail exchange in a way similar to mechanisms for trading items in a marketplace.